Hydraulic control for powershift transmission

Abstract

A method for controlling a transmission includes using signals of first solenoids to control first and second clutches, servos of first gears and servos of second gears, using signals of a second solenoid to establish a flow rate to cool the clutches and to actuate the servo that is associated with a selected gear, and using signals of a third solenoid to direct the flow rate to one of the clutches and to engage the selected gear.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates generally to a powertrain for a motor vehicle, particularly to the hydraulic control circuit of powershift transmission located in the powertrain.[0003]2. Description of the Prior Art[0004]A dual clutch transmission (DCT), also called a powershift transmission, is a geared mechanism employing two input clutches used to produce multiple gear ratios in forward drive and reverse drive. It transmits power continuously using synchronized clutch-to-clutch shifts.[0005]The transmission incorporates gearing arranged in a dual layshaft configuration between the transmission input and its output. One input clutch transmits torque between the input and a first layshaft associated with certain gears; the other input clutch transmits torque between the transmission input and a second layshaft associated with the other gears. The transmission produces gear ratio changes by alternately engaging a first input clu...

AI Technical Summary

Benefits of technology

[0012]The use multiplexed on / off solenoids reduces cost of the control system compared to the cost of conventional variable force solenoids.

[0013]The electro-hydraulic control includes stand-alone, clutch control VFSs, allowing greater independence between clutch control and synchronizer selection. The control has a dedicated VFS for synchronizer flow and pressure control, and synchronizer selection is a result of the valve selection network, which receives input signal from the clutch solenoids and clutch cooling control solenoids.

Problems solved by technology

Due to engine downsizing and boosting for a given vehicle size, boost is not present at launch causing potentially insufficient transmission gear ratio for launching.

A powershift transmission generally has a specific number of gears and provides little design flexibility for accommodating an increase in the number of gears to five, six or seven speeds.

Some designs have relied on multiplexing clutch controls with synchronizer control in an attempt to deduce cost, which results in reduced operating performance, such as longer shift period, loss of repeatable high quality shifts, and an increased number of failure states.

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